The essential oils of citric fruits constitute complex mixtures of organic compounds which interfere with pesticide residues quantitation. As there exists scarce bibliography on ortho-phenylphenol (OPP) determination in this commodity, the present work aims to adapt, develop and validate a simple and cheaper method for determining phenylphenol residues in citrus essential oil, while certifying it under IRAM 301 standard (ISO/IEC 17025:2005). Citrus fruit analysis methods were used, taking advantage of OPP acidity for its extraction from the commodity by simple acid-base extraction. Later, gas chromatography with flame ionization detector (GC-FID) was used for detection and quantitation. Average recoveries were the following: 89% to 104% within the range of 0.1 mg/kg to 100 mg/kg for lemon essential oil; 93% to 103% and 90% to 114%, for white and red grapefruit, respectively, within the range of 0.2 -10 mg/kg. Detection limits were 0.05 mg/kg for lemon essential oil and 0.1 mg/kg for both white and red grapefruit essential oils. Quantitation limits were 0.1 and 0.2 mg/kg for lemon and grapefruit essential oils, respectively. Also, an acceptable linearity was observed in the evaluated ranges and relative uncertainties of 24%, 14% and 23% for lemon, white and red grapefruit essential oils, respectively, were obtained.